1. Field of the Invention
The present invention relates generally to analogue circuits and in particular to gain control circuits.
2. Description of Related Art
In many electronics systems where weak signals generated by sensors or transducers are captured, amplification is required at the front end of the systems to increase the signal strength for further processing of the information carried by such signals. For example, known voltage multipliers make use of voltage buffers to convert the input signal voltage to corresponding signal voltage. In some occasions, the signal conversion is preferably accompanied with gain adjustment for different signal strengths. The gain for weak signals are arranged to be higher than the gain for strong signals. Through such distortion, a high resolution of weak signals can be achieved while keeping strong signal within the dynamic range. The foregoing gain adjustment can be performed in an automatic manner by utilizing devices that can offer controlled impedances, for example, diodes through current drive. However, additional buffer circuitry is needed to enhance the output drive of the pre-amplification stage.
Front-end amplifiers with current feedback configuration are also used for pre-amplification to convert signals from voltage to current representation. Nevertheless, the configuration generally operates within a limited bandwidth that cannot meet the high data rate requirement of modern applications such as audio processing, video processing, and wireless communications.
Consequently, a need exists for an improved gain control circuit that can overcome the forgoing disadvantages and provide wide bandwidth, wide dynamic range, low voltage operation and high efficiency for input signal buffering.